An inkjet head is a liquid drop discharge head used in an ink-jet printing device provided as an image recording device or an image forming device, such as a printer, a facsimile or a copier. The ink-jet head includes a nozzle which discharges the ink drop, a liquid chamber (also called pressurized liquid chamber, pressure chamber, discharge chamber, ink passage, etc.) which communicates with the nozzle for free passage, and a pressure generating means which generates the pressure to pressurize the ink in the liquid chamber. The ink drop is discharged from the nozzle by pressurizing the ink in the liquid chamber by the pressure generated by the pressure generating means.
As for other liquid drop discharge heads, for example, the liquid drop discharge head which discharges the liquid resist as the liquid drop, and the liquid drop discharge head which discharges the sample of DNA as the liquid drop are known.
In addition, as the micro device, for example, the actuator (or the optical switch) of a micro pump, the micro optical array, the micro switch (or the micro relay), and the multiple optical lens, the micro flow meter, the pressure sensor, etc. are known.
A description will be given of the ink-jet head as the example of representation.
There are three major types of the ink-jet heads: piezoelectric type, thermal type, and electrostatic type. The piezoelectric type discharges the ink drop by carrying out deformation and displacement of the diaphragm which forms the surface of a wall of the liquid chamber using electromechanical transducers, such as piezoelectric elements, as the pressure generating means. The thermal type discharges the ink by generating the bubble through the ink boiling using electro-thermal conversion elements, such as the heating resistors arranged in the liquid chamber. The electrostatic type discharges the ink drop by deforming the diaphragm through the electrostatic force using the diaphragm (or the integrally formed electrode) which forms the surface of a wall of the liquid chamber, and its opposing electrode.
In a conventional ink-jet head, the liquid chambers and the common liquid chamber which communicates with the respective liquid chambers are formed with the material, such as a photosensitive resin, a resin mold, metal or glass. However, since the rigidity of resin is insufficient, it is likely that the cross talk between the neighboring liquid chambers takes place, and there is the problem that the picture quality deteriorates.
Moreover, the rigidity of metal or glass is sufficient, and the problem of the cross talk does not take place. However, the manufacture processes of the metal or glass liquid chambers is difficult to perform. Further, for the conventional inkjet head, it is becoming difficult to meet the recent demand for the ink-jet head having a high-density liquid chamber in order to attain good quality of a reproduced image.
Japanese Patent No. 3141652, Japanese Laid-Open Patent Application Nos. 7-276626 and 9-226112 disclose an ink-jet head in which the liquid chambers and the common liquid chamber are formed by the anisotropic etching of a silicon substrate (silicon wafer). The rigidity of silicon is high and the manufacturing processes thereof can be performed easily by using the anisotropic etching. The formation of a perpendicular surface of the liquid chamber wall is possible by using the silicon wafer of (110) crystalline orientation, and this makes it possible to configure the high-density liquid chamber.
When the silicon is used for the liquid-chamber formation member, it is necessary to form the plural liquid chambers and the common liquid chamber corresponding to the head chips on the silicon substrate (silicon wafer), and to separate the silicon substrate into the respective chips.
In this case, as a method of separating the silicon wafer into the chips, the dicing is generally used.
In the dicing, the cutter blade in which diamond powders are attached to the circumference thereof is rotated at high speed and moved along the cutting line, so that the silicon wafer is cut into chips.
For example, Japanese Laid-Open Patent Application No. 10-157149 discloses a silicon dicing method in which the adhesion of chippings in the dicing is eliminated. In the method of the above document, a predetermined separation pattern mask is formed on the silicon wafer, and anisotropic etching is performed so that the wafer is separated into chips by the V-shaped grooves.
Japanese Laid-Open Patent Application No. 5-36825 discloses another silicon dicing method in which the adhesion of chippings in the dicing is eliminated. In the method of the above document, the first and second V-shaped grooves are formed on the silicon wafer, and the concentrated stress is applied the first and second V-shaped grooves so that the wafer is separated into chips by the V-shaped grooves.
However, when performing the chip separation by the conventional dicing method, the cutting line is straight as shown in FIG. 27, and the respective chips 201 must be configured in the lattice formation on the silicon wafer 200. Depending on the size and form of the chip, the restrictions will be in the layout, and the non-used portion of the wafer will be increases. The number of the chips produced from a piece of silicone wafer will be decreased, and the manufacturing cost will be increased.
Moreover, the respective chips can be arranged with the same size only, and it is impossible to produce simultaneously the chips with different sizes.
On the other hand, the anisotropic etching method separates the silicon wafer into chips, and the degree of freedom of the layout of the chips on the wafer becomes large. There are the advantages that the chips with different configurations can be arranged on the same wafer, and that increasing the number of the chips produced is possible by arranging the chips in a staggered formation.
However, when bonding the chip after the separation to other parts, it is necessary that the edge of the chip is brought into contact with the other parts in alignment. In this case, it is required that the edge of the chip is placed with good precision. However, when the separation is performed by anisotropic etching, the precision of the chip edge will no longer be ensured.
That is, when the separation is performed by anisotropic etching, the chip edge will be tapered, like a knife edge, due to crystal orientation, and good precision is not obtained.
When the thickness of the wafer has variations, the chip edge also varies and the precision of the edge deteriorates since the chip edge is tapered. Furthermore, the chip edge is tapered, and the precision of the edge deteriorates due to cracking during production.
Depending on crystal orientations of silicon, the straight-line edge is obtained by anisotropic etching. The reason that the straight-line edge is as follows. In a silicon wafer of (100) crystalline orientation, there are two <110> orientations which are intersected perpendicularly. However, in a silicon wafer of (110) crystalline orientation, there are two <112> orientations or two <110> orientations which are not intersected perpendicularly. In the latter case, the silicon wafer cannot be separated into rectangular or square chips.
When it is desired to separate the silicon wafer of (110) crystalline orientation into rectangular or square chips, the method of arranging the pattern in the shape of a straight line and forming the separation line may be used. However, in this case, the edge of the resulting chip becomes saw-like, or the projection is formed thereon, and such edge is unsuitable for alignment and it may produce particles. The quality of the bonding of the chip to the diaphragm or the nozzle plate deteriorates due to the particles.
Moreover, when separating the wafer by anisotropic etching and etching separates into the chips completely, there is also the problem that the resulting chips are separated apart in etching liquid. In this case, the collection of the chips is difficult. To avoid the problem, the V groove which does not penetrate the separation line is formed so that the wafer may not be separated into chips completely.
However, the silicon wafer in which the separation line is formed by anisotropic etching has very small hardness, and there is a possibility that the wafer is damaged during the subsequent process or conveyance.
Moreover, when separating the wafer into the chips, it pushes with the roller and the stress is applied, and the wafer is separated by the cleavage. Like an electronic device, the chip of a size below several square millimeters can be produced by the separation cutting along with the separation line formed by anisotropic etching. However, as for the micro device which is a comparatively large chip in which the through holes are formed or sub-chips of various sizes are arranged therein, it is likely that the chip is damaged due to a concentrated stress.